Customer had proxy in use, and that was raising proxy errors even though we knew ports were not binding.

"BaseXmlHttpCallback Exception: System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 127.0.0.1:50121
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
at Altiris.DotNetLib.Sockets.SecureRemoting.SecureRemotingClient.EstablishConnection()

The following proxy errors were found misleading for port binding issue.

Module: AtrsHost.exe
Source: Altiris.TaskManagement.ClientTask.*
Description: NotificationServerWebConnection.FigureOutCredentials(): Credentials in Agent registry were invalid, or there was an error connecting to the server.